Securency was found to have profited from a “highly lucrative” deal with the Nigerian national bank involving the sale of plastic used to print banknotes. The bribing of an official at Nigeria’s mint was said to have led to orders of €30 million ($47 million) for Securency.

Chapman was arrested in Brazil after bribing the Nigerian bank’s staff to the tune of a reported £143,000 ($282,000). The British businessman spent six months in one of Rio de Janeiro’s most notorious prisons before being extradited to the UK to face trial.

But at the time Chapman’s case was being considered by the jury, former British Prime Minister Cameron was caught on camera saying that Nigeria was a “fantastically corrupt” country.

“We’ve got some leaders of some fantastically corrupt countries coming to Britain,” Cameron said as a side comment to the British Queen ahead of an anti-corruption summit.

“Nigeria and Afghanistan, possibly the two most corrupt countries in the world.”

Chapman’s lawyers are now arguing that the timing of the gaffe resulted in their client getting an unfair trial.

Chapman, who served most of his jail sentence while awaiting trial, appeared before the Court of Appeal on Friday. Judges will now decide whether the case can proceed.

During the original hearing, the comments were read out in court with Judge Michael Grieve warning the jury that Cameron’s observation could risk prejudicing their decision.